last revised: Sep./12th/2002
$BA0@a$GJQ?t$N@k8@$H=i4|2=$K$D$$$F$^$H$a$^$7$?$,!"K\@a$G$O0[$J$k7?F1;N$NJQ49$K$D$$$F8+$F$_$^$7$g$&!#(B
$BF1$87?$NJQ?tF1;N$OBeF~=PMh$^$9!#(B
double p = 3.1415; double circle = p;
$B$3$NNc$G$O!"JQ?t(B p
$B$K$O?t!J%j%F%i%k!K$,BeF~$5$l$F$*$j!"JQ?t(B circle
$B$K$OJQ?t(B p
$B$,BeF~$5$l$F$$$^$9!#$3$N$H$-!"(B circle
$B$K$O!"(B p
$B$KBeF~$5$l$F$$$kCM$,BeF~$5$l$k$3$H$K$J$j$^$9!#JQ?t$KJQ?t$rBeF~$9$k$H$-$O!"1&JU$NJQ?t$,J];}$9$kCM$,!":8JU$NJQ?t$K%3%T!<$5$l$k$H9M$($FNI$$$G$7$g$&!#(B
$B4pK\%G!<%?7?JQ?tF1;N$NBeF~$G$O!"1&JU$NJQ?t$NCM$,!":8JU$NJQ?t$K%3%T!<$5$l$^$9!#$3$N$H$-!"JQ?t$rJL$N7?$NJQ?t$KBeF~$9$k$H$-$K$O!"7?JQ49$,I,MW$G$9!#(B
$B7?$K$OBg$-$5$,$"$j$^$9!#2^$NLp0u$NJ}8~$K7?$N%5%$%:$OBg$-$/$J$j$^$9!#(B
byte -> short -> int -> long -> float -> double char ->
$B>.$5$$7?$rBg$-$$7?$KBeF~$9$k$H$-$O<+F0E*$K7?JQ49$5$l$^$9!J3HD%JQ49!K!#(B
int i = 10; float f = i; // int $B7?$O(B float $B7?$KBeF~2DG=(B char c = 'a'; int i = c; // char $B7?$O(B int $B7?$KBeF~2DG=(B
$BNc$($P!"(Bbyte $B7?$O(B short, int, long, float, double $B7?$KBeF~2DG=$G$9!#(Bchar $B7?$O(B int, long, float, double $B7?$KBeF~2DG=$G$9!#(B
$B5U$K!"Bg$-$$7?$r>.$5$$7?$KBeF~$9$k$H$-$O!"1i;;@:EY$NDc2<$,5/$3$k$?$a!"<+F07?JQ49$O$5$l$^$;$s!#L@<(E*$J7?JQ49$G$"$k(B$B%-%c%9%H(B$B$,I,MW$G$9!J=L>.JQ49!K!#(B
VarTest.java
:
class VarTest {
public static void main(String[] args) {
int i = 10;
short s;
s = i; // Error!
}
}
C:\>cd java C:\Java>javac VarTest.java VarTest.java:5: $B@:EY$,Mn$A$F$$$k2DG=@-(B $B=P8=(B: int $BMW5a(B: short s = i; // Error! ^ $B%(%i!<(B 1 $B8D(B C:\Java>
$BNc$($P!"(Bdouble $B7?$O(B byte $B7?$K<+F07?JQ49$5$l$^$;$s!#(B int $B7?$O(B char $B7?$d(B short $B7?$K<+F07?JQ49$5$l$^$;$s!#0lHL$K!"3HD%7?JQ490J30$O<+F07?JQ49$5$l$^$;$s!#(B
$B%j%F%i%k$K$b7?$,$"$j!"$=$NBeF~$KBP$7$F$b7?%A%'%C%/$,9T$o$l$^$9!#%j%F%i%k$N7?$O!"4JC1$K8@$&$H
$B%j%F%i%k$NJQ?t$X$NBeF~$b!"JQ?tF1;N$NBeF~$H$[$\F1$8$G$9!#
int i = 'c'; // char $B7?$O(B int $B7?$KBeF~2DG=(B float d = 10L; // long $B7?$O(B float $B7?$KBeF~2DG=(B
$B$?$@0lE@$@$10[$J$j!"@0?t%j%F%i%k$N@0?t7?$X$NBeF~;~$K$O!"=L>.7?JQ49$G$b<+F0E*$K7?JQ49$5$l$^$9!#$9$J$o$A!"
byte b = 10; // 10 $B$OId9fIU@0?t%j%F%i%k$J$N$G(B int $B7?(B
$B$3$N$h$&$K@0?t$,<+F0E*$K=L>.7?JQ49$5$l$k$N$O!"%j%F%i%k$K8B$C$?$3$H$G$9!#JQ?tF1;N$NBeF~$N>l9g$O!"0J2<$N%3!<%I$O8m$j$G$9!#(B
int i = 10; byte b = i; // $B%3%s%Q%$%k%(%i!<(B
$B0l$D$N<0Cf$K0[$J$k7?$,:.:_$9$k$H$-$b!"<+F0E*$J7?JQ49$,5/$3$j$^$9!#7?$,<+F0E*$KJQ49$5$l$k:]$N=gHV$O!"BeF~;~$N7?JQ49$HF1$8$G!">.$5$$7?$,Bg$-$$7?$K<+F07?JQ49$5$l$F1i;;$5$l$^$9!#(B
char
, byte
, short
$B$O(B int
$B7?$K9g$o$;$i$l$k!J@0?t3HD%!K(BVarTest.java
:
class VarTest { public static void main(String[] args) { int i = 100; double d = 3.14; // (int $B!_(B double) $B$N7k2L$O(B double $B$@$H2ri * d); } }
C:\Java>javac VarTest.java C:\Java>java VarTest 314.0 C:\Java>
$B1i;;;~$N7?JQ49$G$b@0?t7?$OFCJL07$$$5$l$F$*$j!"@0?t7?$O<0Cf$G:GDc$G$b(B int $B7?$K>:3J(B (promote) $B$5$l$k$N$G!"
byte b1 = 10, b2 = 5; byte b3 = b1 * b2; // $B%3%s%Q%$%k%(%i!$B$h$/4V0c$($kNc$,
int i = 1988; double d1 = i * 105/100; double d2 = i * 1.05; // => $B@5$7$$7k2L(B double d3 = i / 100 * 105;d1 $B$O(B 2087.0 $B!"(B d2 $B$O(B 2087.4 $B!"(B d3 $B$O(B 1995.0 $B$H$J$j$^$9!#(Bd1 $B$N<0Cf$K$O(B int $B7?$7$+8=$l$F$$$J$$$N$G!";;=Q>:3J$N5,B'>e!"0l@Z$N7?JQ49$,H/@8$7$^$;$s!#:G8e$K(B d1 $B$KBeF~$9$k$H$-$@$1(B double $B7?$K>:3J$7$^$9!#(Bd2 $B$N<0Cf$K$O(B double $B7?$,4^$^$l$F$$$^$9!#Fs9`1i;;;R$N1i;;BP>]$N7?$,Bg$-$$$[$&$K<+F07?JQ49$5$l$k$N$G!"<0$N7k2L$O(B double $B7?$K$J$j$^$9!#:G8e$N(B d3 $B$O:#2s$N%F!<%^$H$O0[$J$j$^$9$,!"!V3d$C$F$+$i3]$1$k$h$j$b!"3]$1$F$+$i3d$C$?$[$&$,NI$$!W$H$$$&Nc$G$9!#:G=i$K(B i / 100 $B$,7W;;$5$l$F!"(B 19.88 -> 19 $B$H$J$j!"$3$l$K(B 105 $B$r3]$1$F$$$k$N$G7k2L$O$H$F$b$_$9$\$i$7$/$J$C$F$$$^$9!#(B
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